Shrink labels of oriented polystyrene film containing small rubber particles and low rubber particle gel content and block copolymers

ABSTRACT

A polymer composition containing (a) a high impact polystyrene (HIPS) component with a block copolymer grafted to polystyrene, a rubbery conjugated diene content of one to seven weight percent based on HIPS weight, less than 10 weight-percent gel concentration, an average rubber particle size of between one and 0.01 micrometers, about 40 to about 90 volume percent of the rubber particles have diameters of less than about 0.4 microns and from about 10 to about 60 volume percent of the rubber particles have diameters between about 0.4 and about 2.5 microns, a majority of rubber particles with a core/shell morphology and a concentration that accounts for 10 to 70 weight-percent of the total polymer composition weight and one to five weight-percent rubbery diene based on total polymer composition weight; (b) from 10 to 70 weight percent of a general purpose polystyrene and from about 2 to about 80 weight-percent of a styrene block copolymer component, both based on total polymer composition weight. In a film, preferably oriented, wherein the polymer composition accounts for at least 95 weight-percent of the film, with the balance of the film or film composition weight being additives. Shrink labels are made from the film.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to oriented rubber-reinforced polystyrenefilm that has a preferential orientation in the stretched direction anda shrink-label film comprising such a polystyrene film as well as acomposition useful for making such films.

2. Description of Related Art

Shrink labels generally fall into two categories: roll-on shrink-on(ROSO) labels and sleeve-type labels; sleeve labels are also sometimesreferred to as tube labels. ROSO labels are film sheets that wrap arounda container. Sleeve labels are tubular in configuration and fit around acontainer by placement over the container, such that the container issurrounded by the tube. Application of heat to a shrink label that isaround a container causes the label to shrink and conform to thecontainer.

To conform to a container, each type of label must shrink preferentially(that is, to a greater extent than in any other direction) in thedirection extending circumferentially around the container. ROSO filmsusually reside on a container with the machine direction (MD) of thefilm extending circumferentially around the container. Hence, ROSO filmsprimarily shrink in the film's machine direction (MD) due topreferential machine direction orientation (MDO). In contrast, sleevelabels usually reside on a container with the label's transversedirection (TD) extending circumferentially around the container. Hence,sleeve labels shrink primarily in the film's transverse direction (TD)due to preferential transverse direction orientation (TDO).

While ROSO labels offer advantages in production speed, sleeve labelshistorically have enjoyed an advantage in extent of shrinkage around acontainer. Sleeve labels typically shrink up to 70 percent (%) aroundthe circumference of a container. Sleeve labels, which either have noglue joint or have a glue joint that is extensively cured prior toapplication to a container, can tolerate a greater extent of stressduring shrinkage.

Sleeve labels historically enjoy more extensive shrinkage and thereforehave conformed better to contoured containers than ROSO labels. However,ROSO labels have a production advantage of being oriented in the machinedirection, that is the direction they travel through machinery usedduring their production. It, therefore, desirable to identify anoriented film suitable for preparing a ROSO label that can shrinkcircumferentially around a container to a greater extent thanpolypropylene ROSO labels but preferably without the detriment offailure at the glue joint of the label.

Polystyrene (PS) is a particularly desirable polymer for shrink labels.Shrink label films of polypropylene (PP), for example, typically shrinkonly up to about 20% in any direction at a temperature below 120° C. Thecrystalline nature of PP requires heating above the PP's crystallinemelt temperature to release additional orientation. In contrast,PS-based shrink label films only need to exceed the polymer's glasstransition temperature (which generally is lower than PP's crystallinemelt temperature) due to its amorphous character. Therefore, PS filmscan desirably provide greater shrink at lower processing temperaturesthan PP films.

Additionally, PS retains a higher surface energy after corona treatment(typically needed to render the surface of a polymer film suitable forprinting) for extended periods of time relative to PP. Therefore, unlikePP films, corona treatment of PS films can occur during manufacturerather than just prior to printing into labels.

In contrast to copolyester and polyvinyl chloride (PVC) films, use of PSfilms facilitate bottle and label recyclability, as the lower densityallows the label to be easily separated from the higher density (forexample, polyester) bottles. Furthermore, the lower PS densityadvantageously provides a higher film yield, or more area/lb. or kg offilm. Higher density labelstock, such as copolyester or PVC films, donot provide similar advantages.

Polystyrene-based shrink label films can include a high impactpolystyrene (HIPS) component in order to improve label toughness (forexample, tear resistance). However, rubber particles in a typical HIPSrange have an average particle size of greater than one micrometer (see,for example, U.S. Pat. No. 6,897,260, column 4, lines 26-27). Largerubber particles tend to decrease clarity of a label film, interferingwith the use of the film for reverse side printing (printing on the sideof a label film proximate to the container so that it is readablethrough the film) as well as with viewing of the container or productthrough the label. Typical HIPS also contains greater than 7 percentrubber based on total HIPS weight. High concentrations of rubber canhinder the printability of a film, decrease clarity of a film, reducedimensional stability and undesirably increase gel amount in a finalfilm. However, in some situations such as small diameter bottles orbottle necks, HIPS alone may not supply sufficient toughness to avoid atendency to split under stress.

It is desirable to have an oriented PS film that is suitable for shrinklabel applications. It is further desirable for the film to contain ahigh impact polystyrene of a type that has smaller rubber particles andlower rubber concentrations than that of typical HIPS in order toachieve film toughening without substantially hindering printability orclarity of the film. It is further desirable for the film to containclear impact resistant polystyrene based on block copolymer technologyto further improve film toughness. It is still further desirable if sucha film can serve as a shrink label that demonstrates circumferentialshrink around a container comparable to that achieved with PVC orpolyester.

BRIEF SUMMARY OF THE INVENTION

The present invention advances shrink-label art by providing an orientedpolystyrene-based film suitable for use as a shrink label and thatcontains HIPS with a rubber particle size and rubber concentration belowthat of typical HIPS, as well as an polystyrene block copolymer forimproved toughness, impact resistance or a combination thereof, and ageneral purpose polystyrene. The present invention can provide arubber-reinforced polystyrene film, and shrink label comprising such afilm, that surprisingly has one or more of high clarity, adequatestiffness for high speed printing as indicated by preferred ranges of 1%secant modulus both MD and TD from 90,000 to 300,000 lb/in² (620 to 2070MPa), and high shrinkage in the direction of stretching as demonstratedby preferred ranges of shrink ratio from 20 to 80% in the primarystretched direction when measured in free air at 110° C. for 10 minutes.

In a first aspect, the present invention is a polymer composition, saidpolymer composition consisting of: (a) At least one high impactpolystyrene (HIPS) component having: (i) a block copolymer of styreneand a rubbery conjugated diene, wherein the copolymer is grafted to apolystyrene; (ii) optionally, two weight-percent or more and 8weight-percent or less of a rubber homopolymer based on the HIPScomponent weight; (iii) a total rubbery conjugated diene content of oneweight percent or more and seven weight percent or less based on totalweight of the HIPS component; (iv) less than 10 wt % gel concentrationby methyl ethyl ketone/methanol extraction; (v) an average rubberparticle size of less than 1.0 micrometers and 0.01 micrometers or more;(vi) about 40 to about 90 volume percent of the rubber particles withdiameters of less than about 0.4 microns and from about 10 to about 60volume percent of the rubber particles with diameters between about 0.4and about 2.5 microns; (vii) a majority of rubber particles with acore/shell morphology; (viii) and that is present at a concentration ofat least about 10 weight percent and up to at most about 70 weightpercent of the polymers in the composition and accounts for one or moreand five or less percent by weight of rubbery diene weight relative tototal composition weight; and (b) at least one general purposepolystyrene having a weight-average molecular weight of more than200,000 grams per mole and 350,000 grams per mole or less and that ispresent at a concentration of at least about 10 weight percent and up toat most about 50 weight percent of the polymers in the composition; and(c) at least one styrene block copolymer that is present at aconcentration of at least about 2 weight percent and up to at most about80 weight percent of the polymers in the composition; (a), (b) and (c)account for 100 percent by weight of the polymers in the polymercomposition. This polymer composition is optionally admixed withadditives within the skill in the art up to about 5 weight percent ofthe combined weight of polymer composition and additives to make a filmcomposition, that is a composition suitable for making films.

In a second aspect the invention is an oriented film consisting 95 to100 weight percent the polymer composition of the invention and 0 to 5weight percent additives where the percentages are based on the combinedweight of polymers and additives; and wherein preferably the film has aratio in the primary direction stretched (usually MDO for ROSO or TDOfor sleeve applications) of more than 4:1, more preferably 6:1 and aratio in the direction of less stretch of 1.2:1 or less and wherein theratio in the direction that received more stretch is greater than theratio in the other direction.

In a third aspect, the present invention is a shrink label comprising aaxially unbalanced oriented polymer film (that is, a film having adifferent amount of orientation in the MD than in the TD) of the firstaspect wherein the film preferably has printing on one or both sides.The shrink label is preferably either a ROSO or a sleeve label, mostpreferably a sleeve label.

DETAILED DESCRIPTION OF THE INVENTION

Films of the present invention comprise a polymer composition comprisinga HIPS component, a general purpose polystyrene (GPPS), and a styreneblock copolymer component. The combination of the HIPS component, GPPSand styrene block copolymer component account for 100 percent by weight(wt %) of the polymers in the composition aside from additives, that isthe polymer composition. The polymer composition desirably accounts for95 wt % or more, preferably 97 wt % or more, and can comprise 100 wt %of the total weight of the film composition or the film. When thepolymer composition is less than 100 wt % of the film weight, thebalance to 100 wt % consists of additives, including any additives thatmay be part of the HIPS component, GPPS, and styrene block copolymercomponents as obtained commercially or by manufacture. Additives includefillers, processing aids, slip agents, or plasticizers within the skillin the art and optionally include polymeric additives.

All percentages, preferred amounts or measurements, ranges and endpointsthereof herein are inclusive, that is, “less than about 10” includesabout 10. “At least” is, thus, equivalent to “greater than or equal to,”and “at most’ is, thus, equivalent “to less than or equal to.” A number“or more” is equivalent to “at least” that number. Similarly. “or less”after a number is equivalent to “at most” the number. Numbers hereinhave no more precision than stated. Thus, “105” includes at least from104.5 to 105.49. Furthermore, all lists are inclusive of combinations oftwo or more members of the list. All ranges from a parameters describedas “at least,” “greater than,” “greater than or equal to” or similarly,to a parameter described as “at most,” “up to,” “less than,” “less thanor equal to” or similarly are preferred ranges regardless of therelative degree of preference indicated for each parameter. Thus a rangethat has an advantageous lower limit combined with a most preferredupper limit is preferred for the practice of this invention. Allamounts, ratios, proportions and other measurements are by weight unlessstated otherwise. All percentages refer to weight percent based on totalcomposition according to the practice of the invention unless statedotherwise, except that percentages of monomers in a polymer are weightpercentages unless stated otherwise. Unless stated otherwise orrecognized by those skilled in the art as otherwise impossible, steps ofprocesses described herein are optionally carried out in sequencesdifferent from the sequence in which the steps are discussed herein.Furthermore, steps optionally occur separately, simultaneously or withoverlap in timing. For instance, such steps as heating and admixing areoften separate, simultaneous, or partially overlapping in time in theart. Unless stated otherwise, when an element, material, or step capableof causing undesirable effects is present in amounts or in a form suchthat it does not cause the effect to an unacceptable degree it isconsidered substantially absent for the practice of this invention.Furthermore, the terms “unacceptable” and “unacceptably” are used torefer to deviation from that which can be commercially useful, otherwiseuseful in a given situation, or outside predetermined limits, whichlimits vary with specific situations and applications and may be set bypredetermination, such as performance specifications. Those skilled inthe art recognize that acceptable limits vary with equipment,conditions, applications, and other variables but can be determinedwithout undue experimentation in each situation where they areapplicable. In some instances, variation or deviation in one parametermay be acceptable to achieve another desirable end.

The term “comprising”, is synonymous with “including,” “containing,” or“characterized by,” is inclusive or open-ended and does not excludeadditional, unrecited elements, material, or steps. The term “consistingessentially of” indicates that in addition to specified elements,materials, or steps; elements, unrecited materials or steps may bepresent in amounts that do not unacceptably materially affect at leastone basic and novel characteristic of the subject matter. The term“consisting of” indicates that only stated elements, materials or stepsare present. The term “comprising” is inclusive of “consistingessentially of” and “consisting of.”

The HIPS component is a styrene polymer containing a grafted rubbercomponent. Grafting of a rubber component into a polystyrene tends toincrease toughness and mechanical strength of the polystyrene. Bindingthe rubber to the polystyrene through grafting has technical advantagesover simply blending polystyrene with a rubber component. Binding therubber generally provides a material with a higher modulus andequivalent impact strength with a lower rubber content than a simplyblended rubber. Graft the rubber component into the styrene polymer bycombining the rubber component with styrene monomers, typically bydissolving the rubber in styrene monomers prior to polymerizing thestyrene monomers. Polymerizing the styrene monomers then produces amatrix of polystyrene containing rubber grafted to styrene polymers.

The polystyrene matrix typically has a sufficiently high weight averagemolecular weight (Mw) to provide a desirable level of processability andmechanical properties in the composition, which is typically a Mw of atleast 100,000, preferably at least about 120,000, more preferably atleast about 130,000 and most preferably at least about 140,000 grams permole (g/mol). The polystyrene typically has a Mw that is less than orequal to about 260,000, preferably less than or equal to about 250,000,more preferably less than or equal to about 240,000 and most preferablyless than or equal to about 230,000 g/mol in order to provide sufficientprocessability. Measure polystyrene matrix Mw by using gel permeationchromatography using a polystyrene standard for calibration.

The rubber component is a copolymer of a rubbery conjugated diene andstyrene (rubber copolymer) or a blend comprising both the rubbercopolymer and a minor amount of a rubbery conjugated diene homopolymer(rubber homopolymer). The conjugated diene in both rubbers is typicallya 1,3-alkadiene, preferably butadiene, isoprene or both butadiene andisoprene, most preferably butadiene. The conjugated diene copolymerrubber is preferably a styrene/butadiene (S/B) block copolymer.Polybutadiene is a desirable rubber homopolymer.

The rubber copolymer desirably has a Mw of 100,000 g/mol or more,preferably 150,000 g/mol or more and desirably 350,000 g/mol or less,preferably 300,000 g/mol or less, more preferably 250,000 g/mol or less.Measure Mw using Tri Angle Light Scattering Gel PermeationChromatography.

The rubber copolymer also desirably has a solution viscosity in therange of from about 5 to about 100 centipoise (cP) (about 5 to about 100milliPascal-second (mPa*s)), preferably from about 20 to about 80 cP(about 20 to about 80 mPa*s); and cis content of at least 20%,preferably at least 25% and more preferably at least about 30% anddesirably 99% or less, preferably 55% or less, more preferably 50% orless. Buna BL 6533 T brand rubber and other similar rubbers aredesirable examples of rubber copolymers.

Including rubber homopolymer with a rubber copolymer when preparing theHIPS component can contribute to the mechanical performance of the HIPSpolymer by enhancing the amount of elongation at rupture. Suitablerubber homopolymers desirably have a second order transition temperatureof zero degrees Celsius (° C.) or less, preferably −20° C. or less.Preferably, the rubber homopolymer has a solution viscosity in the rangeof about 20 to about 250 cP (about 20 to about 250 mPa*s), morepreferably from about 80 cP to 200 cP (about 80 to about 200 mPa*s). Therubber homopolymer desirably has a cis content of at least about 20%,preferably at least about 25% and more preferably at least about 30% anddesirably about 99% or less, preferably 55% or less, more preferably 50%or less. Desirably rubber homopolymers have a Mw of 100,000 g/mol ormore, more preferably 150,000 g/mol or more and desirably 600,000 g/molor less, preferably 500,000 g/mol or less. Measure Mw by Tri Angle LightScattering Gel Permeation Chromatography). An example of a suitablerubber homopolymer is Diene™ 55 brand rubber (Diene is a trademark ofFirestone).

Rubber homopolymer, when present, will typically comprise at least about2 wt %, preferably at least about 4 wt %, more preferably at least about6 wt % and most preferably at least about 8 wt % based on total rubberweight in the HIPS polymer. In order to avoid unnecessarily lowtransparency or clarity, the rubber homopolymer content is desirably 25wt % or less, preferably 20 wt % or less, more preferably 16 wt % orless and most preferably 12 wt % or less based on total rubber weight.

The HIPS component has a total diene-component content from the rubbercomponent (that is, content arising from rubbery conjugated diene ofboth rubber copolymer and rubber homopolymer when preparing the HIPScomponent) of about one wt % or more, preferably 1.5 wt % or more, morepreferably 2 wt % or more, still more preferably 2.5 wt % or more andmost preferably 3 wt % or more based on weight of the HIPS component.Rubber concentrations below about 1 wt % fail to obtain a desirablelevel of mechanical strength and toughness. In order to providedesirable transparency, the rubber concentration is typically 7 wt % orless, preferably 6 wt % or less, more preferably 5 wt % or less, evenmore preferably 4 wt % or less, based on total weight of the HIPScomponent.

Without being bound by theory, lower rubber concentrations, such as 7 wt% or less based on HIPS, is desirable to avoid extensive crosslinking inthe rubber particle and reduce the likelihood of gel formation. Whilesome crosslinking in the rubber is desirable to maintain the integrityof the rubber during shearing in manufacture, extensive crosslinking canhinder a rubber particle's ability to deform during film orientation.Clarity and transparency of a film increase as rubber particles deforminto particles with higher aspect ratios. Rubber particles with lesscrosslinking tend to deform and retain their deformed shape more readilythan higher crosslinked rubber particles, making the lower crosslinkedparticles more amenable to clear and transparent films. Defining aspecific rubber concentration where crosslinking becomes undesirablyextensive is difficult since it depends on specific processingconditions. Even so, rubber concentrations of 12 wt % or more based onHIPS weight, tend to have undesirably extensive crosslinking.

Similarly, without being bound by theory, films of the present inventionlikely benefit from having a lower gel formation as a result of a lowerrubber concentration. Gels form by extensive crosslinking of rubberagglomerates which fail to shear into small particles during filmmanufacture. Crosslinked gel agglomerates can cause difficulty in filmmanufacture, for instance by causing bubble breaks in a blown filmprocess. Gel agglomerates also have a detrimental effect on filmquality, appearing as non-uniform defects in the film and causingdimples in films wound over the agglomerate particle. The dimples tendto pose problems during printing by precluding ink reception on dimpledspots of a film's surface.

The HIPS component further has a gel concentration according to a methylethyl ketone/methanol extraction of less than 10 wt %, relative to totalHIPS component weight. Such a low gel concentration is desirable tomaximize film clarity. Conduct the methyl ethyl ketone/methanolextraction similar to the method of Unexamined Japanese PatentApplication Kokai No. P2000-351860A for determining gel concentration.In essence, dissolve a sample of the HIPS (sample weight is W1) into amixed solvent methyl ethyl ketone/methanol (10:1 volume ratio) at roomtemperature (about 23° C.). Separate the insoluble fraction bycentrifugal separation. Isolate and dry the insoluble fraction. Theweight of the isolated and dried insoluble fraction is W2. The gelconcentration in wt % is 100×W2/W1.

The HIPS component has a volume average rubber particle size of lessthan one micrometer (μm), preferably 0.5 μm or less and generally 0.01μm or more, preferably 0.1 μm or more and more preferably 0.3 μm ormore. Such a volume average rubber particle size is in contrast toconventional HIPS materials, which have an average rubber particle sizeof at least one μm (see, for example, U.S. Pat. No. 6,897,260B2, column4, lines 22-34; which illustrates the skill in the art and isincorporated herein by reference to the fullest extent permitted bylaw). Small rubber particle sizes are desirable because they tend toproduce films with higher clarity and lower haze than films with largerrubber particles. However, rubber particles below 0.01 μm tend tocontribute little to the durability of a composition despite theirtransparency and clarity.

The rubber particles in the HIPS component have a broad particle sizedistribution where the majority of the particles are smaller and only alimited amount of particles are larger. In particular, it is desirableto have a distribution where from about 40 to about 90 volume percent(vol %) of the particles have diameters less than about 0.4 μm.Correspondingly, it is desirable to have a distribution of relativelylarge particles where from about 10 to about 60 vol % of the particleshave diameters greater than about 0.4 μm and less than about 2.5,preferably from about 15 to 55 vol % and more preferably from about 20to about 50 vol % of the particles have diameters greater than or equalto about 0.5 μm and less than or equal to about 2.5 μm. Preferably, forthis component of relatively large particles, the specified percentageamounts of the particles have diameters less than about 2 μm, morepreferably about 1.5 μm or less, still more preferably about 1.2 μm orless, even more preferably about 1 μm or less.

Rubber particle size is a measure of rubber-containing particles,including all occlusions of monovinylidene aromatic polymer within therubber particles. Measure rubber particle size with a Beckham Coulter:LS230 light scattering instrument and software. The manufacturer'sinstructions and literature (JOURNAL OF APPLIED POLYMER SCIENCE, VOL. 77(2000), page 1165, “A Novel Application of Using a Commercial FraunhoferDiffractometer to Size Particles Dispersed in a Solid Matrix” by Jun Gaoand Chi Wu) provide a method for measuring rubber particle size with theBeckham Coulter. Preferably, using this equipment and software, theoptical model for calculating the rubber particle size and distributionstatistics is as follows: (i) Fluid Refractive Index of 1.43, (ii)Sample Real Refractive Index of 1.57 and (iii) Sample ImaginaryRefractive Index of 0.01.

The majority of the rubber particles, preferably 70% or more, morepreferably 80% or more, more preferably 90% or more of the rubberparticles in the HIPS component will have a core/shell particlemorphology. Core/shell morphology means that the rubber particles have athin outer shell and contain a single, centered occlusion of a matrixpolymer. This type of particle morphology is commonly referred to as“single occlusion” or “capsule” morphology. In contrast, the terms“entanglement” or “cellular” morphology refer to various other, morecomplex rubber particle morphologies that include “entangled”, “multipleocclusions”, “labyrinth”, “coil”, “onion skin” or “concentric circle”structures. Determine the percentage of rubber particles having acore/shell morphology as a numerical percentages from 500 particles in atransmission electron micrograph photo of the HIPS component.

Core-shell particles in the HIPS component are crosslinked to the degreethat they will stretch but not break under shear fields (that is, duringan orientation process). Their thin walls (as a result of highcompatibility coming from the presence of copolymer rubbers) will becomeeven thinner but remain intact to provide the needed mechanical andtensile strength properties. Presumably, upon film orientation, theoriented rubber morphology is very close to a co-continuous distributionof very thin ribbons of rubber, possibly as a result of a low amount ofmulti-occlusion particles in the system (cellular morphology). The verythin shell walls have better light transmittance than would result withthicker walls and definitely better than if there were residual cellularor multi-occlusion particles, which do not distribute as very thinribbons upon orientation.

The HIPS component is optionally free of or optionally contains otheradditives such as mineral oil or other plasticizers. Appropriate amountsof mineral oil can improve mechanical properties such as elongation atrupture. The HIPS component will typically contain at least about 0.4 wt%, preferably 0.6 wt % or more, more preferably 0.8 wt % or more andstill more preferably 1 wt % or more mineral oil based on total weightof the HIPS component. In order to obtain a desirable clarity, the HIPScomponent will generally contain less than about 3 wt %, preferably 2.8wt % or less, more preferably 2.6 wt % or less and most preferably 2.4wt % or less mineral oil based on total weight of the HIPS component.

A suitable material for use as the HIPS component is that described inU.S. Pregrant Publication 2006-0084761 entitled: IMPROVED RUBBERMODIFIED MONOVINYLIDENE AROMATIC POLYMERS AND THERMOFORMED ARTICLES.

The HIPS component differs from standard, mass or solution polymerizedHIPS in that the rubber particle size distribution is relatively broadand the majority of the rubber particles have a core-shell morphology.In contrast, conventional HIPS resins tend to have a relatively narrowparticle size distribution and have predominantly or at least a largerpercentage of cellular, multi-occlusion particle structure.

Compositions and films of the present invention contain preferably atleast about 10, more preferably at least about 20, most preferably atleast about 25 and at most preferably at most about 70, more preferablyat most about 65, most preferably at most about 60 weight percent basedon total amount of polymer present of the HIPS component.

Total rubber content (based on total diene content from copolymer andhomopolymer) arising from the HIPS component in the films of the presentinvention is 1 wt % or more, preferably 3 wt % or more and 5 wt % orless based on total film weight.

The polymer composition of the present film contains a crystalpolystyrene, also called a general purpose polystyrene (GPPS). GPPS foruse in the present invention desirably has a Mw of more than 200,000g/mol, preferably 280,000 g/mol or more and 350,000 g/mol or less,preferably 320,000 g/mol or less. Measure Mw using to gel permeationchromatography and a known standard. The GPPS desirably has a melt flowrate (MFR) of one or more, preferably 1.2 grams per 10 minutes (g/10min) or more and desirably 3 g/10 min or less, preferably 2 g/10 min orless. Measure MFR according to ASTM method D1238. The GPPS may be freeof or may contain plasticizing agents such as mineral oil, ethylene orpropylene glycol, phthalates, or styrenic oligomers. Plasticizingagents, when present, are typically present at a concentration of 4 wt %or less, preferably 3 wt % or less, based on GPPS weight. When present,the plasticizing agent typically comprises one wt % or more of the GPPSweight. Examples of suitable GPPS include STYRON® 665 general purposepolystyrene (STYRON is a trademark of The Dow Chemical Company), STYRON663, STYRON 685D, STYRON 660, and STYRON 6856E.

Compositions and films of the present invention contain preferably atleast 10, more preferably at least about 20, most preferably at leastabout 35, and at most preferably at most about 50, more preferably atmost about 45, most preferably at most about 40 weight percent based ontotal amount of polymer present of the GPPS component.

The third component of the formulation is at least one styrene blockcopolymer. The term “styrene block copolymer or styrenic blockcopolymer” means a polymer having at least one block segment of astyrenic monomer in combination with at least one saturated orunsaturated rubber monomer segment, and more preferably not having ablock of polymer that is neither rubber or styrenic. Suitable styreneblock copolymers having unsaturated rubber monomer units include, butare not limited to, styrene-butadiene (SB), styrene-isoprene (SI),styrene-butadiene-styrene (SBS), styrene-isoprene-styrene (SIS),α-methylstyrene-butadiene-α-methylstyrene,α-methylstyrene-isoprene-α-methylstyrene, and the like. The term“styrene butadiene block copolymer” is used herein inclusive of SB, SBSand higher numbers of blocks of styrene and butadiene. Similarly, theterm “styrene isoprene block copolymer” is used inclusive of polymershaving at least one block of styrene and one of isoprene. The structureof the styrene block copolymers useful in the present invention can beof the linear or radial type, and of the diblock, triblock or higherblock type. In some embodiments the styrenic block copolymers having atleast four different blocks or a pair of two repeating blocks, forexample, repeating styrene/butadiene or styrene/ethylene propyleneblocks, are desirable. Styrene block copolymers are well within theskill in the art and are commercially available from Dexco Polymersunder the trademark VECTOR, from KRATON Polymers under the trademarkKRATON, from Chevron Phillips Chemical Co. under the trademark SOLPRENEand K-Resin, and from BASF Corp. under the trade designation Styrolux.The styrene block copolymers are optionally used singly or incombinations of two or more.

The styrenic portion of the block copolymer is preferably a polymer orinterpolymer of styrene or its analogs or homologs, includingα-methylstyrene, and ring-substituted styrenes, particularlyring-methylated styrenes. Preferred styrenics are styrene andα-methylstyrene, with styrene being especially preferred.

The rubber portion of the block copolymer is optionally eitherunsaturated or saturated. Block copolymers with unsaturated rubbermonomer units may comprise homopolymers of butadiene or isoprene andcopolymers of one or both of these two dienes with a minor amount ofstyrenic monomer. When the monomer employed in butadiene, it ispreferred that between about 35 and about 55 mole percent of thecondensed butadiene units in the butadiene polymer block have a1,2-configuration. When such a block is hydrogenated, the resultingproduct is, or resembles, a regular copolymer block of ethylene and1-butene (EB). If the conjugated diene employed is isoprene, theresulting hydrogenated product is or resembles a regular copolymer blockof ethylene and propylene (EP). Preferred block copolymers haveunsaturated rubber monomer units, more preferably including at least onesegment of a styrenic unit and at least one segment of butadiene orisoprene, with SBS and SIS most preferred. Among these, styrenebutadiene block copolymers are preferred when a cast tenter line is usedin manufacturing a film because it has higher clarity and lower haze ascompared to SIS. However, in blown film processes, styrene isopreneblock copolymers are preferred because of a lower tendency to crosslinkforming gels during manufacture as compared to SBS.

Among styrene block copolymers, those which have one, preferably two ormore preferably all three of clarity, impact resistance and elastomericbehavior are preferred.

Elastomeric styrene block copolymers are preferred in the practice ofthe present invention to provide toughness and lower stiffness thanwould be obtained in the absence of the block copolymer. Elastomericbehavior is indicated by a property of tensile percent elongation atbreak of advantageously at least about 200, preferably at least about220, more preferably at least about 240, most preferably at least about260 and preferably at most about 2000, more preferably at most about1700, most preferably at most about 1500 percent as measured by theprocedures of ASTM D-412 and/or D-882. Industrially, most polymers ofthis type contain 10-80 wt % styrene. Within a specific type andmorphology of polymer, as the styrene content increases the elastomericnature of the block copolymer decreases.

The block copolymers desirably have a melt flow rate (MFR) of at leastabout 2, preferably at least about 4 grams per 10 minutes (g/10 min) anddesirably at most 20 g/10 min, preferably at most 30 g/10 min. MeasureMFR according to ASTM method D1238 Condition G.

Preferred styrene block copolymers are highly transparent (have high,that is preferred ranges of, clarity), preferably having clarity whenmeasured by ASTM D1746 corresponding to at least about 85%, preferablyat least about 90% transmission of visible light. This transparency isbelieved to be due to the very small domain size, which is typically ofthe order of 20 nm. In block copolymers the domain sizes are determinedprimarily by block molecular weights.

The styrene block copolymers also are preferably sufficiently impactresistant to add durability in film applications as compared to thedurability of films having the same composition (proportion ofcomponents) except without the styrene block copolymers. Notched IzodImpact resistance is measured according to the procedures of ASTM D-256and preferably gives a no break condition when tested at 72° F. or 23°C.

A particularly preferred styrene butadiene block copolymer has a radialor star block configuration with polybutadiene at the core andpolystyrene at the tips of the arms. Such polymers are referred toherein as star styrene butadiene block copolymers and are within theskill in the art and commercially available from Chevron PhillipsChemical Co. under the trade designation K-Resin. These polymers containabout 27% butadiene or more in a star-block form and often feature abimodal molecular weight distribution of polystyrene. The innerpolybutadiene segments are of about the same molecular weight while theouter polystyrene segments are of different molecular weight. Thisfeatures facilitates control of polybutadiene segment thickness, toobtain improved clarity. For high clarity, the polybutadiene segmentthickness is preferably about one-tenth of the wavelength of visiblespectrum or less.

The styrene block copolymer component is useful for improving toughnessand lowering stiffness over that of a composition having the othercomponents but not the block copolymer. However, incorporation of highamounts of a styrene-isoprene-styrene component can tend to obscure theclarity and transparency of the films. The styrene block copolymer ispresent in an amount preferably of at least about 2 weight percent ofthe polymers in the film or composition, more preferably at least about3, most preferably at least about 4, preferably at most about 80, morepreferably at most about 75, most preferably at most about 70 weightpercent based on weight of the polymers in the film or blend(composition) used to make the film. Within these preferred amounts,when the block copolymer is a styrene-butadiene block copolymer, that ispreferably SB or SBS, the amount is preferably at least about 20, morepreferably at least about 30, most preferably at least about 40 andpreferably at most about 80, more preferably at most about 75, mostpreferably at most about 70 weight percent based on total weight ofpolymers in the film or composition. More than about 80 weight percentstyrene butadiene block copolymer tends to decrease the 1% secantmodulus and glass transition temperature undesirably, possibly such thatthe film shrinks at low temperatures, for instance below about 80° C.However, because SIS and SIS/SI may result in haze when in amounts ofabout 10 weight percent or more, lower percentages of styrene-isopreneblock copolymer component are preferred. The amount of styrene isopreneblock copolymer, when present, is preferably at least about 1, morepreferably at least about 2, most preferably at least about 3, andpreferably at most about 9, more preferably at most about 8, mostpreferably at most about 6 weight percent based on total weight ofpolymers in the blend or film. These amounts are preferred whether theSIS or SI block copolymers are used alone or with other styrene blockcopolymers.

Films of the present invention have orientation with preferentialorientation in the direction that receives the most stretch as the filmis formed or processed. The resulting film shrinks preferentially in thedirection that was stretched more as the film was manufactured. Machinedirection (MD) is along the direction of film transport during or afterextrusion or blowing of the film. Transverse direction (TD) isperpendicular to the direction of film transport (MD). Shrinkage ispreferentially machine direction orientation (MDO) if more stretch isapplied to the MD than to the TD, and TDO if more stretch is appliedtransverse than machine direction. Preferential TDO causes a film of thepresent invention to shrink primarily in the TD upon application ofheat, for instance in a sleeve label. Preferential MDO results ingreater shrink in the machine direction than in the TD as is usuallyused for ROSO labels.

Films of the present invention have an MDO or TDO ratio (ratio oforiented length to un-oriented length in the direction most stretched,MD or TD, respectively) advantageously of at least about 3:1, preferablyat least about 4:1, more preferably at least about 5:1, still morepreferably at least about 6:1. Films typically have a TDO ratio greaterthan their MDO ratio in order to be useful in shrink tube labelapplications or MDO ratio greater than TDO ratio in order to be usefulin ROSO label films. Films having a TDO for sleeve applications or MDOfor ROSO applications of less than 3:1 tend to have insufficientdirectional orientation (DO), either MDO or TDO depending on the use, toconform to a container in a shrink label application. There is no clearupper limit for DO ratio, although films typically have a DO ratio of10:1 or less. Films having an DO ratio greater than 10:1 risk shrinkingaround a container in a label application to such an extent that a glueseam holding the label around the bottle can weaken or fail.

Measure MDO ratio and TDO ratio by using an oriented film sample 4″(10.16 cm) in both MD and TD (that is, square samples). Place the samplein a heated air oven at 120° C. for 10 minutes and then measure MD andTD dimensions again. The ratio of pre- to -post-heated MD and TDdimensions correspond to MDO ratio and TDO ratio, respectively.

Films of the present invention desirably demonstrate a shrinkage at 110°C., preferably at 100° C., of at least about 20%, preferably at leastabout 30%, advantageously at least about 40%, preferably at least about50%, more preferably at least about 60%, most preferably at least about70% in the more stretched direction. Shrinkage below 20% tends toundesirably limit the extent to which a film can conform to a containercontour. While an upper limit on the extent of directional shrink isunknown, it will be below 100%.

Desirably, the films demonstrate a opposite directional shrinkage at100° C., preferably at 110° C. of at least about 5%, more preferably atleast about 7, most preferably at least about 10 percent in thedirection of least shrink. Films having a shrink in the direction ofless shrink of less than about 5% tend to suffer from poor integrityupon handling and fracture upon bending. Therefore, some orientation andshrink is desirable to enhance film integrity. Extensive shrink in theless stretched direction hinders the film's performance in shrink labelapplications by resulting in contraction of the film and, hence,distortion of the label in the other direction. Therefore, films of thepresent invention typically have an orientation ratio in the lessstretched direction at most about 1.2:1, preferably at most about1.15:1, corresponding to a shrink of at most about 20%, preferably atmost about 15%.

Films of the present invention further desirably demonstrate no morethan about 10% increase in length (growth) in the direction opposite themain shrink direction in the direction opposite primary stretch at 110°C., preferably at 100° C. (Films that shrink more than 20% or grow morethan 10% in that direction at the specified temperatures tend tocomplicate conformation of a film to a container in shrink labelapplications due to distortions in that direction.) Measure shrinkageaccording to ASTM method D-1204. Films of the present invention furtherdesirably demonstrate relatively low growth in the direction notpurposely stretched, or direction less stretched, in test methodsaccording to U.S. Pat. No. 6,897,260 B2.

The presence of the HIPS component provides films of the presentinvention with a desirable high clarity and transparency while at thesame time enhancing the toughness of the films. Clarity and transparencyare desirable in the label industry to provide a non-obscured view of aproduct around which the label resides. High clarity and transparencyare also desirable for “reverse” printing of labels where printingresides between the label and the container and a consumer views theprinting through the label. Typically, films of the present inventionhave clarity values at a film thickness of 2.0 mils (50 μm) of at leastabout 10, advantageously at least about 15, preferably at least about20, more preferably at least about 25, most preferably at least about 30when prepared on commercial equipment, that is, equipment used tomanufacture commercial label films. Those skilled in the art recognizethat thicker films will have less clarity than thinner films of the samecomposition made the same way. Measure clarity according to ASTM methodD-1746.

Haze values also provide a measure of a film's observed clarity, withlow haze corresponding to high clarity. Haze values for films of thepresent invention can range to any conceivable value. However, oneadvantage of the present invention is the ability to obtain orientedfilms with high clarity and low haze. Typical haze values for thepresent films at a film thickness of 2.0 mils (50 μm) are at most about15, preferably at most about 10, more preferably at most about 6, mostpreferably at most about 4. Measure haze according to ASTM methodD-1003.

A styrene-based film advantageously has a higher secant modulus than,for example, oriented polypropylene or oriented polyvinyl chloridefilms. Increasing the secant modulus of a shrink label film is desirableto hinder the films likelihood of stretch during printing. As a result,films of the present invention can run at faster print speeds withoutrisk of film breakage or distortion relative to a film with a lowersecant modulus without the HIPS component. Films of the presentinvention have a one percent secant modulus in both the MD and TD of atleast about 90,000 pounds-per-square-inch (psi) (620 MegaPascals (MPa)),preferably at least about 100,000 psi (690 MPa), more preferably atleast about 200,000 psi (1,380 MPa). Measure one percent secant modulusby American Society for Testing and Materials (ASTM) method D-882.

Similar to films with high secant modulus, films with a high tensilestress at break, particularly in the MD, are desirable so that films canrun faster and under higher tension in printing processes withoutstretching than films with a lower tensile stress. Desirably, films ofthe present invention have a tensile stress at break of at least about2,000 psi (14 MPa), preferably at least about 2,500 psi (17 MPa), morepreferably at least about 3000 psi (21 MPa) and most preferably at leastabout 4,000 psi (28 MPa). Measure tensile stress at break by ASTM D-882.

Films with a high tensile strain at break are desirable to allowprinting and handling of the films with high speed processing equipmentwithout splitting the film. Desirably, films of the present inventionhave a tensile strain at break in both directions of testing of at leastabout 30 percent, preferably at least about 35 percent, more preferablyat least about 40 percent and most preferably at least about 45 percent.Measure percent strain at break by ASTM D-882. Desirably, films of thepresent invention have a toughness as measured by the procedures of ASTMD-882 of at least about 2,000 psi (14 MPa), preferably at least about2,500 psi (17 Mpa), more preferably at least about 3000 psi (21 Mpa) andmost preferably at least about 4,000 psi (28 Mpa).

Films of the present invention generally have a thickness of at leastabout one mil (25 μm), preferably at least about 1.5 mils (38 μm) andgenerally at most about 4 mils (100 μm), preferably at most about 3 mils(76 μm). At a thickness of less than one mil (25 μm), films tend to beundesirably difficult to cut during processing and handling. Thicknessesgreater than 4 mils (100 μm) are technically achievable, but generallyeconomically undesirable.

Films of the present invention desirably have an orientation releasestress (ORS) of 400 psi (2758 kPa) or less. ORS is a measure of thestress the film experiences during shrinkage upon heating. Lowering ORSvalues in a shrink film is desirable. Shrink films typically have atleast one end glued to a container around which the film is applied.Labels with high ORS values can apply sufficient stress to a glue seamholding the label around a container during shrinkage so as to damage orbreak the seam. Lowering ORS values decreases the likelihood that theseam line (film on film) becomes damaged or broken during shrinkage.

Prepare films of the present invention by any means of oriented filmmanufacture including blown film process and cast-tentering processes.Particularly desirable are blown film processes such as those describedin U.S. Pat. No. 6,897,260 and Great Britain Patent (GBP) 862,966 (bothof which are incorporated herein by reference).

To avoid unintended crosslinking, processing temperatures and residencetimes should be minimized. Melt temperatures are preferably below about230° C., preferably below about 220° C., more preferably below about210° C. The higher the process melt temperature the shorter the polymercan be kept at that temperature before unacceptable degradation. Forinstance, exposure to temperatures in excess of about 230° C. ispreferably limited to less than about 10 minutes, more preferably lessthan about 7 minutes, most preferably less than about 300 seconds.

One suitable process (“Process A”) for preparing films of the presentinvention is a blown film process using an apparatus as described inU.S. Pat. No. 6,897,260 or GBP 862,966. Feed polymer pellets to theapparatus and convert them to a polymer melt having a temperature withina range of from 170° C. to 100° C.; then cool the polymer melt to atemperature within a range of from 130° C. to 170° C. to increase meltviscosity before extruding the polymer melt through a blown film dieinto a gaseous atmosphere. Maintain the gaseous atmosphere at atemperature at least 40° C. below the heat distortion temperature of theeach polymer composition component(s) (HIPS component and if presentGPPS and/or styrene block copolymer component) in the polymer melt. Blowthe extruded polymer melt according to the bubble process of GBP862,966.

Another possible blown film process (“Process B”) suitable for preparingfilms of the present invention uses two extruders (Extruder 1 andExtruder 2) in series. Extruder 1 is a 2½ inch (6.35 cm) diameter, 24:1single screw extruder with five barrel zones, each set at a temperaturebetween 155° C. and 200° C., typically increasing in temperature downthe extruder. Extruder 2 is a 3½ inch (8.89 cm) diameter, 32:1 singlescrew with a barrier mixing screw and five barrel zones, each havingtemperature set point typically at a temperature from 115° C. and 175°C. Feed polymer pellets into Extruder 1 to plasticize the polymer andpump the polymer to Extruder 2 at a temperature of 200-260° C. Thepolymer proceeds from Extruder 1 through a transfer line and into theentry port of extruder 2. Cool the polymer in Extruder 2 to a melttemperature (extrusion temperature) of selected between 150-190° C. soas to achieve a stable bubble and to optimize orientation release stress(ORS) properties of the resulting film to a desirable value. Cool thepolymer by cooling the walls of Extruder 2. Extrude the polymer fromExtruder 2 through a 3.25 inch (8.3 cm) annular die and then through a4.5 inch (11.4 cm) diameter air ring and blow or expand the polymer intoa bubble with a diameter that typically ranges from 9 inches (22.9 cm)to 24 inches (63.5 cm). Use the bubble blowing process of GBP 862,966.

In another embodiment, a preferred process for preparing the films is acast tentering method (“Process C”). First a film or sheet is cast, thatis a self-supporting film or sheet is formed from a melt supplied by anextrusion system. The resin is extruded through a slit as a flat sheet,approximately 0.3-2.5 mm thick, onto a cooled, smooth cast roll at atemperature of from about 30 to about 70° C.) to form a monolayer film.The cast roll speed is adjusted to result in the thickness of film tofrom about 0.3 to about 1 mm thick. This film or sheet carried byrollers into a heated chamber containing a tenter frame. Air in thechamber is heated sufficiently to heat the film or sheet enough topermit stretch without tearing, at a temperature depending oncomposition of the film, approximately about 95° C. to about 150° C. Atenter frame has two side-by-side endless chains that diverge atconstant angle. The film is held onto the chains by film clips.Divergence of the chains forces the polymer to stretch as it istransported along the chain, and imparts the desired orientation.Stretch rate is determined by the chain speed, divergence angle, andextent of orientation. The extent of orientation is determined by theratio of the width of the film entering to the width of the film leavingthe system to achieve amounts of stretch and corresponding shrinkdescribed previously. This imparts primarily TD orientation. The film isthen annealed, if desired, and released. In most instances, edges of thefilm are slit off, ground, and recycled, and the film is optionallywound full width or split into narrower widths, which are optionallytreated to improve printability and then wound onto rolls for furtherprocessing. If desired, machine direction orientation is imparted to theextent previously described, either by machine direction orientation bysuccessively faster rollers at any stage when the film or sheet issufficiently warm to permit stretch, such as when the film or sheet isformed and before quenching, when heated for TD orientation or in aseparate step.

Films of the present invention have utility in any application thatbenefits from heat triggered shrinkage. The films have a particularutility as shrink labels. To convert a film of the present inventioninto a shrink label of the present invention, cut the film to adesirably width and corona treat a side of the film (in any order) andthen print on the corona treated side of the film. Printing can resideon the “reverse” side of the film to create a reverse printed label. Thereverse side of the film resides against a container and printing on thereverse side is viewed through the film when the film is around acontainer in a shrink label application. These steps are typically doneon a continuous web process by any method useful in the art.

Films and labels of the present invention can also advantageouslypossess perforations through the film or label. Perforations are mostdesirably located in the portion of a film proximate to the narrowestportion or portions of a container around which the film is applied. Theperforations allow gas that would otherwise tend to become trappedbetween the label and container to escape, thereby allowing the label tomore tightly conform to the container. Films, and labels, of the presentinvention can contain perforations uniformly distributed across a filmsurface or contain perforations specifically located proximate to theareas of the film (or label), advantageously to the area that willcoincide with the narrowest portions of a container around which thefilm (or label) will reside. Perforation of films and labels of thepresent invention can be perforated at any time; however, in order tofacilitate printing of labels, desirably perforate films and labelsafter printing.

Objects and advantages of this invention are further illustrated by thefollowing examples. The particular materials and amounts thereof, aswell as other conditions and details, recited in these examples shouldnot be used to limit this invention. Unless stated otherwise allpercentages, parts and ratios are by weight. Examples of the inventionare numbered while comparative samples, which are not examples of theinvention, are designated alphabetically.

HIPS-X Component for Examples 1-4 and Comparative Samples B AND D

Examples 1-4 and Comparative Samples B and D, hereinafter, utilizeHIPS-X as the HIPS component. Produce HIPS-X, for example, in thefollowing continuous process using three agitated reactors working inseries. Prepare a rubber feed solution by dissolving the rubbercomponents of Table 1 into styrene at a rubber component ratio of 1 partDiene 55 to 15 parts Buna 6533 (that is, 0.3 wt % Diene 55 and 4.5 wt %Buna 6533 based on total rubber feed solution weight). Incorporate 2.5wt % mineral oil (70 centistokes kinematic viscosity) and 7 wt % ethylbenzene with the rubber feed solution to form a feed stream, with wt %relative to total feed stream weight. Add 0.1 wt % Antioxidant Irganox1076 to provide levels of about 1200 parts per million (ppm) in thefinal product. The balance of the feed is styrene to 100 wt %. Supplythe feed stream to the first reactor at a rate of 750 grams per hour(g/h). Target a rubber blend content in the feed stream and the feedrates of styrene and rubber to a reactor to produce a rubber-modifiedpolystyrene product (HIPS-X) containing 4 wt % butadiene.

Each of the three reactors has three zones with independent temperaturecontrol. Use the following temperature profile: 125, 130, 135, 143, 149,153, 157, 165, 170° C. Agitate at 80 revolutions per minute (RPM) in thefirst reactor, 50 RPM in the second reactor and 25 RPM in the thirdreactor. Add 100 ppm of chain transfer agent (n-Dodecyl Mercaptan ornDM) into the second zone of the first reactor.

Use a devolatilizing extruder to flash out residual styrene andethylbenzene diluent and to crosslink the rubber. The temperatureprofile for the devolatilizing extruder is 240° C. at the start of thebarrel, medium zone of the barrel and final zone of the barrel. Thescrew temperature is 220° C.

Use the following test methods (or methods defined previously herein) tocharacterize HIPS-X: Melt Flow Rate: ISO-133. PS Matrix molecular weightdistribution: PS calibration Gel Permeation Chromatography. RubberParticle size: Light scattering using an LS230 apparatus and softwarefrom Beckman Coulter. Tensile Yield, Elongation and Modulus: ISO-527-2.

Determine the gel concentration of HIPS-X by methyl ethyl ketoneextraction. For analyzing HIPS-X, dissolve a 0.25 gram sample of HIPS-Xinto a methyl ethyl ketone/methanol mixture (10:1 volume ratio) byplacing the sample and mixture into a tube of known weight and agitatingon a wrist shaker for two hours at room temperature (23° C.). Isolate aninsoluble fraction by placing the tube in a high speed centrifuge andspinning at 19500 revolutions per minute at 5° C. for one hour. Decantoff excess liquid and place the tubes in a vacuum oven at 150° C. for 45minutes at a vacuum of 2-5 millimeters of mercury. Remove the tubes fromthe oven and allow to cool to approximately 23° C. Weigh the tubes todetermine, subtract the known weight of the tube to determine gelweight. The gel weight divided by 0.25 grams and multiplied by 100provides the wt % gel content relative to total HIPS-X weight.

TABLE 1 Conjugated Diene Conjugated Diene Copolymer rubber HomopolymerRubber Property Buna BL 6533 T Diene 55 (Trademark of (trademark ofBayer) Firestone) Styrene Content (%) 40 0 Vinyl Content (%) 9 11 CisContent (%) 38 38 Viscosity (Mooney 45 70 viscosity ML1 + 4 100° C. inPascal-Seconds) Solution Viscosity (5.43% 40 170 in toluene)milliPascal- Seconds Polymer Structure AB Block copolymer Generallylinear

HIPS-X has a volume average rubber particle size of 0.35 μm with 65 vol% of the particle having a size of less than 0.4 μm and 35 vol % of theparticles having a size of 0.4-2.5 μm. HIPS-X has a rubber concentrationof 0.38 wt % butadiene homopolymer and 5.6 wt % styrene/butadienecopolymer, for a combined rubber concentrations of 5.98 wt % based onHIPS-X weight. HIPS-X has a gel concentration of approximately 8 wt %,relative to total HIPS-X weight. HIPS-X contains 2 wt % mineral oil, hasa MFR of 7.0 g/10 min, Vicat temperature of 101° C., Tensile Yield of 20megaPascals (Mpa), elongation at rupture of 25% and tensile modulus of2480 Mpa.

The following materials are used in addition to HIPS-X in the Examplesof the Invention and some Comparative Samples:

-   GPPS-1 is a general purpose polystyrene having a tensile modulus of    greater than 400,000 psi (2750 Mpa) commercially available from The    Dow Chemical Company under the trade designation STYRON™ 665    Polystyrene Resin.-   Block-1 is a styrene-butadiene (SB) block copolymer having diene    content greater than 30 weight percent and flexural modulus of less    than 200,000 (1380 Mpa) commercially available from Chevron-Phillips    Chemical Company under the trade designation K-Resin™ KK38    styrene-butadiene-styrene resin.-   Block-2 is a styrene-isoprene-styrene/styrene-isoprene (SIS/SI)    block copolymer having a styrene content of about 15 weight percent    and a SHORE A hardness of 24 (ASTM D-2240) commercially available    from Dexco Polymers LP under the trade designation VECTOR™ 4114A    Styrene-Isoprene-Styrene/Styrene-Isoprene SIS/SI Styrenic Block    Copolymer.-   Block-3 is a styrene-isoprene-styrene (SIS) block copolymer having a    styrene content of about 18 weight percent and a SHORE A Hardness of    39 commercially available from Dexco Polymers LP under the trade    designation VECTOR® 4111A Styrene-Isoprene-Styrene (SIS) Styrenic    Block Copolymer.-   Block-4 is a thermoplastic styrene-butadiene block copolymer having    a styrene content from 70 to 80 weight percent and a tensile modulus    of 120,000 psi (825 Mpa) commercially available from BASF    Corporation under the trade designation Styrolux™ 3G55 Q420    styrene-butadiene-styrene block copolymer.

Procedure for Examples 1-4 and Comparative Samples B-D

In each of the following examples each component listed in Table 2 is inpellet form, scooped into a tumble blender where the components aremixed for about 2 minutes to form an admixture. No additives are addedbut it is recognized that some of the commercial polymers used maycontain additives as commercially available.

The admixture is placed into each of 3 one inch (2.54 cm) diameterextruders, each having a length to diameter (L/D) ratio of 24:1. Theadmixtures are heated to a temperature of 390° F. (198° C.) by heatersintegral to the extruders. That temperature is maintained until the filmis cast through a die with a 10 inch (25.4 cm) wide slit with a gap of0.040 inches (0.10 cm) onto a water/glycol cooled smooth cast roll at atemperature of 130° F. (54° C.) to form a monolayer film in eachinstance. The cast roll speed is adjusted to result in the thickness offilm listed in each Example or Sample.

The film examples and samples are then cut to 4″ (10.16 cm) squares andstretched with a T. M. Long Film Stretching Machine commerciallyavailable from T. M. Long Co., Inc of Somerville, N.J. The filmstretcher has a sample holder with several edge clamps for each of thefour edges of a sample. Hot air is blown from below onto the sample thatis suspended in air by the clamps. A diverter is below the sample holderto divert the hot air from blowing directly onto the sample. When thediverter is absent hot air blows on the sample. Each film example orsample is heated at an air temperature indicated in Table 2 for oneminute with a diverter in and out for the periods designated in Table 2.Then the sample or example is stretched at a rate of 0.4 inch/second(1.0 cm/s) until the film is stretched 4 times its original dimension inthe transverse direction of extrusion and constrained to no stretch inthe machine direction by edge clamps.

In the Examples and Comparative samples, the air temperatures are variedto avoid tearing of the samples by the edge clamps. The selected airtemperature is selected by a dial indicator on the machine andmaintained by the machine. The length of time the diverter is in or outis selected to avoid tearing the sample during stretching because it hasthe effect of changing the sample temperature.

Examples (Ex) 1-4 and Comparative Samples (C.S.) B.-D

TABLE 2 Weight Percentages of Components and Thickness of Films Exampleor Sample number Ex. 1 Ex. 4 C.S. B Ex. 2 Ex. 3 C.S. C C.S. D HIPS-X wt% 30 50 65 20 60 30 GPPS-1 wt % 30 40 35 20 35 BLOCK-1 wt % 40 60BLOCK-2 wt % 10 BLOCK-3 wt %  5 BLOCK-4 wt % 100  70 thickness 10 mil 15mil 15 mil 15 mil 15 mil 15 mil 15 mil (0.25 mm) (0.38 mm) (0.38 mm)(0.38 mm) (0.38 mm) (0.38 mm) (0.38 mm) Stretch air 125° C. 130° C. 135°C. 125° C. 135° C. 115° C. 130° C. temperature Stretch 30 30 30 30 30 1515 diverter “in” period in seconds Stretch 30 30 30 45 30 15 15 diverter“out” period in seconds All percentages are weight percentages ofpolymers present exclusive of additives except those that may be in thecommercial products as obtained. *Comparative Samples are not examplesof the present invention.

Table 3 illustrates film properties for Ex 1-4 and C.S. B-D. Use thefollowing test methods to characterize films throughout the presentdisclosure. Measure Haze according to the procedures of ASTM methodD-1003. Measure Clarity according to the procedures of ASTM methodD-1746. Measure Tensile Stress and Strain, Toughness and Secant Modulusaccording the procedures of ASTM method D-882. Measure orientationrelease stress (ORS) according to the procedures of ASTM method D-2838.Measure Free Air Shrink according to the procedures of ASTM methodD-1204.

TABLE 3 Properties of Films of Examples 1-4 and Comparative Samples B-D:Property Ex 1 Ex 4 Comp B Ex 2 Ex 3 Comp C Comp D Prestretched 10 15 1515 15 15 15 Thickness, mils Prestretched 254 381 381 381 381 381 381thickness μm thickness, mils 2.50 3.50 4.10 3.90 4.10 3.50 4.30Stretched thickness 64 89 104 99 104 89 109 μm Clarity** 2.70 0.60* 3.261.52 1.26 33.60 3.80 Haze 13.10 43.20* 6.80 11.00 13.00 1.90 18.10Tensile Stress 3,740 3,540 5,490 2,920 3,550 4,620 4,480 at Break, MDpsi Converted to MPa 26 24 38 20 24 32 31 Tensile Stress 7,560 4,8806,360 6,010 6,820 6,050 4,300 at Break, TD psi Converted to MPa 52 34 4441 47 42 30 Tensile Strain 73 81 3 256 54 410 360 at Break, MD % TensileStrain 104 55 53 117 95 160 160 at Break, TD % Toughness, MD, psi 3,0302,890 70 7,240 1,970 10,910 11,080 Converted to MPa 21 20 0 50 14 75 76Toughness, TD, psi 6,080 2,790 3,030 5,220 5,580 6,380 5,510 Convertedto MPa 42 19 21 36 38 44 38 1% Secant Modulus, 158,000 210,000 264,000103,000 161,000 54,000 97,000 MD, psi Converted to MPa 1089 1448 1820710 1110 372 669 1% Secant Modulus, 263,000 263,000 307,000 177,000264,000 62,000 109,000 TD, psi Converted to MPa 1813 1813 2117 1220 1820427 752 Free Air Shrink, 0.0 0.0 0.0 0.0 0.0 −2.9 −1.7 MD 80 C., 10 minFree Air Shrink, 0.0 0.0 0.0 0.0 0.0 28.0 12.2 TD 80 C. 10 min Free AirShrink, 3.9 −2.0 −2.7 −1.6 −2.7 −2.9 −4.7 MD 100 C., 10 min Free AirShrink, 48.9 14.9 27.0 30.3 21.3 62.0 48.0 TD 100 C. 10 min Free AirShrink, 12.6 3.9 1.2 −2.9 −3.3 7.0 2.0 MD 110 C., 10 min Free AirShrink, 63.8 57.2 55.1 66.6 57.1 73 54 TD 110 C. 10 min *It is believed,but not confirmed, that the relatively high haze and lack of clarity ofthis sample may be at least partially the result of one or moreadditives in Block-2 as received. **Clarity obtained using thislaboratory equipment is lower than would be expected for the samecompositions prepared on commercial equipment. It is believed that thisdata indicates that the clarity of Ex. 1, 2 and 3 would be withinpreferred ranges if prepared on commercial equipment.

Examples 1-4 illustrate a variety of formulations within the scope ofthe invention and show that their properties are appropriate for makingshrink labels. Example 4 also illustrates that the use of excess SIS mayresult in more haze than may be desirable for some shrink labels.Comparative Sample B illustrates that the absence of styrene blockcopolymer results in lower MD toughness than is useful for shrink labelsbecause such labels will be observed to split easily along theunstretched direction. Comparative Sample C illustrates that labelswithout HIPS-X have a low modulus, this labels made with such aformulation will be observed to have undesirably low stiffness.Comparative Sample D illustrates that a label without GPPS has more hazethan is desirable for shrink labels.

Comparison of Comparative Sample C and Comparative Sample D shows thatthe addition of HIPS-X to a block copolymer results in higher stiffnessas indicated by higher one percent secant modulus.

Preferred embodiments of the invention include but are not limited to:

1. A film composition comprising from 0 to 5 weight percent additivesand from 95 to 100 weight percent of a polymer composition consistingessentially of:

-   -   (a) At least one high impact polystyrene (HIPS) component        having:        -   (i) a block copolymer of styrene and a rubbery conjugated            diene, wherein the copolymer is grafted to a polystyrene;        -   (ii) optionally, two weight-percent or more and 8            weight-percent or less of a rubbery conjugated diene            homopolymer based on total rubber weight in the HIPS            component.        -   (iii) a total diene-component content from the rubber            component of one weight percent or more and seven weight            percent or less based on total weight of the HIPS component;        -   (iv) less than 10 wt % gel concentration by methyl ethyl            ketone/methanol extraction;        -   (v) an average rubber particle size of less than 1.0            micrometers and 0.01 micrometers or more;        -   (vi) about 40 to about 90 volume percent of the rubber            particles with diameters of less than about 0.4 microns and            from about 10 to about 60 volume percent of the rubber            particles with diameters between about 0.4 and about 2.5            microns;        -   (vii) a majority of rubber particles with a core/shell            morphology;        -   (viii) that is present at a concentration of at least about            10 weight percent and up to at most about 70 weight percent            of the polymers in the composition and accounts for one or            more and five or less percent by weight of rubbery diene            weight relative to total composition weight    -   (b) at least one general purpose polystyrene having a        weight-average molecular weight of more than 200,000 grams per        mole and 350,000 grams per mole or less and that is present at a        concentration of at least about 10 weight percent and up to at        most about 50 weight percent of the polymers in the composition;        and    -   (c) at least one styrene block copolymer having a tensile        elongation at break of advantageously at least about 200 and a        melt flow rate as determined by the procedures of ASTM D1238,        Condition G, of at least about 2 g/10 min and that is present at        a concentration of at least about 2 weight percent and up to at        most about 80 weight percent of the polymers in the composition;        wherein, the total combination of (a), (b) and (c) accounts for        100 wt % of the polymer composition.

2. The composition of Embodiment 1 wherein the styrene block copolymerhas clarity when measured by ASTM D1746 corresponding to at least about85%, preferably at least about 90% transmission of visible light.

3. The composition of Embodiment 1 or 2 wherein one or more of the HIPS,the GPPS, the styrene block copolymer are selected and used in amountseffective to achieve at least one, advantageously at least 2, moreadvantageously at least 3, most advantageously at least 4, preferably atleast 5, more preferably at least 6, most preferably at least 7 of thefollowing when the composition is used to make a film having a thicknesspreferably as designated in the procedure specified for measurement ofthe properties, alternatively at a thickness intended for use,preferably from about 25 or 38 μm to about 76, 100 or 110 μm, morepreferably a stretched thickness of 64, 65, 89, 90, 100, 104, 105, 109,or 110 μm, most preferably a stretched thickness of 50 μm:

(a) a clarity corresponding to that of a 50 μm film of at least aboutany of 10, 15, 20, 25 or 30 as measured according to the procedures ofASTM D-1746;

(b) a haze corresponding to that of a 50 μm film of less than about anyof 15, 10, 6, or 4 as measured according to the procedures of ASTMD-1003;

(c) a 1% secant modulus in MD, TD or, more preferably both, of at leastabout any of 620 MPa, 680 MPa, or 1380 MPa as measured according to theprocedures of ASTM D-882;

(d) a tensile strain at break in the MD, TD or, more preferably both, ofat least about any of 30, 35, 40, or 45 percent as measured according tothe procedures of ASTM D-882;

(e) a tensile stress at break in the MD, TD or, more preferably both, ofat least about any of 14, 17, 21 or 28 MPa as measured according to theprocedures of ASTM D-882;

(f) a toughness in the MD, TD or, more preferably both, of at leastabout any of 14, 17, 21 or 28 MPa as measured according to theprocedures of ASTM D-882;

(g) an orientation release stress less than 2758 kPa as measuredaccording to the procedures of ASTM D-2838.

4. The composition of any of Embodiments 1 through 3, wherein the highimpact polystyrene component has a volume average rubber particle sizeof 0.5 micrometers or less and 0.01 micrometers or more.

5. The composition of any of Embodiments 1 through 4, wherein the amountof (a) HIPS is at least about any of 10, or 25 wt %, at most about anyof 60, 65 or 70 wt %, the (b) GPPS is at least about any of 10, 20 or 35wt %, at most about any of 40, 45 or 50 wt % or (c) styrene blockcopolymer component is at least about 2, 3, or 4 wt %, at most about 70,75 or 80 wt % based total weight of polymer components (a), (b) and (c)or any combination thereof.

6. The composition of any of Embodiments 1-5 wherein the styrene blockcopolymer is at least one styrene butadiene block copolymer and ispresent in an amount of at least about 20, 30, or 40 wt %, or at mostabout 70, 75 or 80 wt % based on total weight of (a), (b) and (c).

7. The composition of any of Embodiments 1-6 wherein the styrene blockcopolymer is at least one styrene isoprene block copolymer and ispresent in an amount of at least about 2, 3, or 4 wt %, or at most about6, 8, or 9 wt % based on total weight of (a), (b) and (c).

8. The composition of any of Embodiments 1-7, wherein the rubberyconjugated diene in the copolymer of (a) is butadiene.

9. The composition of any of Embodiments 1-8, wherein 90 percent or moreof the rubber particles have a particles have a particle size of lessthan 0.4 micrometers and the balance of the rubber particles to 100percent have a particle size of 2.5 micrometers or less.

10. A film comprising the composition of any of Embodiments 1-9.

11. The film of Embodiment 10, wherein the film demonstrates a growth ofless than 10% in the direction of less stretch after 5 minutes in aheated air oven at 110 degrees Celsius.

12. The film of any of Embodiments 10-11 wherein the polymer compositionaccounts for at least 95 wt % of the oriented film weight with thebalance to 100 wt % selected from additives; and wherein the film has adirectional orientation in the direction stretched of at least about3:1.

13. The film of any of Embodiments 10-12, wherein the film has a machinedirection (MD) and transverse direction (TD) one-percent secant modulusper American Society for Testing and Materials method 882 of at leastabout 250,000 pounds per square inch (1,724 MegaPascals).

14. The film of any of Embodiments 10-13, having a thickness preferablyof from about 25 or 38 μm to about 76, 100 or 110 μm, more preferably athickness of any of 64, 65, 89, 90, 100, 104, 105, 109, or 110 μm, mostpreferably a thickness of 50 μm.

15. The film of any of the Embodiments 10-14 at any thickness specifiedin Embodiment having at least one, advantageously at least 2, moreadvantageously at least 3, most advantageously at least 4, preferably atleast 5, more preferably at least 6, most preferably at least 7 of theproperties specified in Embodiment 3.

16. The film of any of Embodiments 10-15 wherein the film has one orboth of (a) a ratio of oriented to unoriented length of in the directionmost stretched of at least about 3:1, 4:1, 5:1 or 6:1 or (b) a ratio oforiented to unoriented length in the direction perpendicular to thedirection of most stretch (also known as direction of least stretch) ofat least about 1.05:1, 1.07:1 or 1.10:1 to at most about 1.2:1 or1.15:1.

17. The film of any of Embodiments 10-16 wherein the film has one orboth of (a) a shrink in the direction most stretched of at least about20, 30, 40, 50, 60, or 70 percent; or (b) a shrink in the direction ofleast stretch of from any of 5, 7 or 10 percent to any of 15 or 20percent.

18. The film of any of Embodiments 10-17 further comprisingperforations.

19. A shrink label comprising an oriented polymer film of any ofEmbodiments 10-18, preferably wherein the film has printing on one orboth sides.

1. A film composition comprising from 0 to 5 weight percent additivesand from 95 to 100 weight percent of a polymer composition consistingessentially of: (a) At least one high impact polystyrene (HIPS)component having: (i) a block copolymer of styrene and a rubberyconjugated diene, wherein the copolymer is grafted to a polystyrene;(ii) optionally, two weight-percent or more and 8 weight-percent or lessof a rubbery conjugated diene homopolymer based on total rubber weightin the HIPS component (iii) a total diene-component content from therubber component of one weight percent or more and seven weight percentor less based on total weight of the HIPS component; (iv) less than 10wt % gel concentration by methyl ethyl ketone/methanol extraction; (v)an average rubber particle size of less than 1.0 micrometers and 0.01micrometers or more; (vi) about 40 to about 90 volume percent of therubber particles with diameters of less than about 0.4 microns and fromabout 10 to about 60 volume percent of the rubber particles withdiameters between about 0.4 and about 2.5 microns; (vii) a majority ofrubber particles with a core/shell morphology; (viii) that is present ata concentration of at least about 10 weight percent and up to at mostabout 70 weight percent of the polymers in the composition and accountsfor one or more and five or less percent by weight of rubbery dieneweight relative to total composition weight (b) at least one generalpurpose polystyrene having a weight-average molecular weight of morethan 200,000 grams per mole and 350,000 grams per mole or less and thatis present at a concentration of at least about 10 weight percent and upto at most about 50 weight percent of the polymers in the composition;and (c) at least one styrene block copolymer having a tensile elongationat break of advantageously at least about 200 and a melt flow rate asdetermined by the procedures of ASTM D1238, Condition G, of at leastabout 2 g/10 min and that is present at a concentration of at leastabout 2 weight percent and up to at most about 80 weight percent of thepolymers in the composition; wherein, the total combination of (a), (b)and (c) accounts for 100 wt % of the polymer composition.
 2. Thecomposition of claim 1 wherein the styrene block copolymer has claritywhen measured by ASTM D1746 corresponding to at least about 85%transmission of visible light.
 3. The composition of claim 1, whereinthe high impact polystyrene component has a volume average rubberparticle size of 0.5 micrometers or less and 0.01 micrometers or more.4. The composition of claim 1, wherein the amount of styrene blockcopolymer component is at least about 3 weight percent based on weightof the polymer composition.
 5. The composition of claim 1 wherein thestyrene block copolymer is at least one styrene butadiene blockcopolymer and is present in an amount of at least about 20 weightpercent based on total polymer composition weight.
 6. The composition ofclaim 1 wherein the styrene block copolymer is at least one styreneisoprene block copolymer and is present in an amount of 2 to 9 weightpercent based on total polymer composition weight.
 7. The composition ofclaim 1, wherein the rubbery conjugated diene in the copolymer of (a) isbutadiene.
 8. The composition of any of claim 1, wherein 90 percent ormore of the rubber particles have a particles have a particle size ofless than 0.4 micrometers and the balance of the rubber particles to 100percent have a particle size of 2.5 micrometers or less.
 9. Thecomposition of claim 1 wherein one or more of the HIPS, the GPPS, thestyrene block copolymer are selected and used in amounts effective toachieve at least 3 of the following when the composition is used to makea film having a thickness designated in the procedure specified formeasurement of the property, or, if the thickness is not specified at athickness of 100 μm: (a) a clarity corresponding to that of a 50 μm filmof at least about any of 10, 15, 20, 25 or 30 as measured according tothe procedures of ASTM D-1746; (b) a haze corresponding to that of a 50μm film of less than about any of 15, 10, 6, or 4 as measured accordingto the procedures of ASTM D-1003; (c) a 1% secant modulus in MD, TD or,more preferably both, of at least about any of 620 MPa, 680 MPa, or 1380MPa as measured according to the procedures of ASTM D-882; (d) a tensilestrain at break in the MD, TD or, more preferably both, of at leastabout any of 30, 35, 40, or 45 percent as measured according to theprocedures of ASTM D-882; (e) a tensile stress at break in the MD, TDor, more preferably both, of at least about any of 14, 17, 21 or 28 MPaas measured according to the procedures of ASTM D-882; (f) a toughnessin the MD, TD or, more preferably both, of at least about any of 14, 17,21 or 28 MPa as measured according to the procedures of ASTM D-882; or(g) an orientation release stress less than 2758 kPa as measuredaccording to the procedures of ASTM D-2838.
 10. A film comprising thecomposition of claim
 1. 11. The film of claim 10, wherein the filmdemonstrates a growth of less than 10% in the direction of less stretchafter 5 minutes in a heated air oven at 110 degrees Celsius.
 12. Thefilm claim 10 wherein the polymer composition accounts for at least 95wt % of the oriented film weight with the balance to 100 wt % selectedfrom additives; and wherein the film has a directional orientation inthe direction stretched of at least about 3:1.
 13. The film of claim 10,wherein the film has a machine direction (MD) and transverse direction(TD) one-percent secant modulus per American Society for Testing andMaterials method 882 of at least about 250,000 pounds per square inch(1,724 MegaPascals).
 14. The film of claim 10 wherein the film has ashrink in the direction most stretched of at least about 50 percent anda shrink in the direction least stretched of from 5 to 20 percent. 15.The film of claim 10, further comprising perforations.
 16. A shrinklabel comprising an oriented polymer film of claim 10 wherein the filmhas printing on one or both sides.
 17. A shrink label comprising anoriented polymer film of claim 11 wherein the film has printing on oneor both sides.
 18. A shrink label comprising an oriented polymer film ofclaim 12 wherein the film has printing on one or both sides.
 19. Ashrink label comprising an oriented polymer film of claim 13 wherein thefilm has printing on one or both sides.
 20. A shrink label comprising anoriented polymer film of claim 14 wherein the film has printing on oneor both sides.